This invention pertains to the art of container transport trailers and more particularly to rolloff dumpster trailers in which a frame is selectively raised relative to an associated tractor for releasing a container from the trailer.
The invention is particularly applicable to a container transport trailer having wheels disposed at one end and a second end of the trailer adapted for connection to a conventional tractor and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other environments and applications.
A rolloff dumpster is a trailer that selectively transports a removable container or box. The container is typically removed from the trailer by raising a frame to a predetermined angle relative to the ground surface so that the container will slide off the frame due to gravity. In the past, a reeving hoist has been employed on the trailer and attached to the container to pull the container onto the frame.
Tractor trailer arrangements in wide use today employ two frames in the rolloff dumpster arrangement. A first frame is a heavy-duty, I-beam chassis that has wheels disposed at one end for transporting the trailer over the road and is secured to the fifth wheel of a tractor at its other end. The first frame maintains its substantially horizontal arrangement at all times, whether it is towed by a tractor or supported by jack stands at the front end of the trailer.
The second frame is selectively pivoted relative to the first frame. In a first or lowered position, the second frame is substantially horizontal and supported along its length by the first frame. In a second or raised position, the second frame remains secured to the first frame at one end and is lifted relative to the first frame at the other end. Double acting telescopic lift cylinders are disposed on the first frame and urge the second frame to pivot about the first end and dispose the second frame at a predetermined lift angle. Rollers are provided on either the second frame or the container, or both, to aid in sliding movement of the container off the second frame. A reeving cylinder winch assembly is then secured to one end of a new container to haul the container onto the second frame. Thereafter, the lift cylinders are retracted and the second frame brought into generally horizontal, mating arrangement with the first frame.
Requirements under various laws limit the size and weight of the trailer. As is apparent from the above discussion, prior arrangements have utilized two separate frames that unnecessarily add to the overall weight of the rolloff dumpster trailer. The materials necessary for manufacturing these trailers are also correspondingly expensive and lead to an overall, unnecessary complexity of construction.
Another problem associated with trailers of this type is the need to control movement of the container relative to the trailer during loading and unloading. Specifically, the container may move approximately 35 feet along the frame during either loading or unloading. It is obviously much safer to control the unloading movement of the container rather than permitting free rolling of the container. On the other hand, it is also necessary to provide a means for moving a container onto the frame. In the past, a variety of winch assemblies have been utilized which are unnecessarily cumbersome and extremely slow to use. A winch assembly is economically undesirable because of its problems with safety and speed. The cables will often break.
Still another concern is the ability of a modified trailer to withstand axial and lateral movement of components of the trailer. Although pivoting movement of the tractor relative to the trailer is provided at the fifth wheel to provide turning movement of the truck, any unnecessary lateral or axial shifting of the trailer components will be transferred to the container. This, in turn, imposes stresses on the container/trailer interconnection.